Strange electrical problem

OK open to ideas here with this one :-

we have a mcb style mains board (crabtree from memory) which has an RCD device built in. Normally when when for an example a bulb goes the trip for that lighting circuit goes bit of a pain but we can live with it. However yesterday and today has been a nightmare with the main breaker tripping on average every two hours! No individual circuit goes and throwing the break brings everything back to normal (apart from having to reset the times on the cooker microwave stero etc!).

At a loss for any ideas. Nothing has changed regarding load no new devices etc and its happened day and night so its not something we are manually turning on or off.

any ideas where to start ?

Reply to
Mano
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Switch off individual breakers and see when/ if the problem goes away. After determining the circuit at fault you can then isolate individual appliances on that circuit until you isolate one that causes the problem to go away. You then attend to that appliance. If you can identify an individual circuit that has problems but no appliance has a problem, then you have wiring/ wiring fitting problems.

If the problem doesn't go away at all using any of the checks above you then, most probably, have a defective MCB.

I think you may have some confusion between the function of an mcb and that of an rcd. The mcb will trip if the circuit current exceeds the value quoted on the mcb, whereas the rcd will trip if the difference in the current flowing in the live and neutral conductors exceeds a minimal value, normally

30 mA (30 thousandths of an ampere). The two devices are intended to protect you against rather different circuit faults and may well be protecting you against fire at this very moment.

Call in a qualified electrician and get it sorted! Don't do any nasty desperate bodges!

Reply to
Tuthledeen

Reply to
Tuthledeen

Not strange, in fact a common problem. Search this group for RCD nuisance trip Start by unplugging all non essential earthed appliances and see if it stops. Tripping individual MCBs and waiting a few hours might eliminate those circuits, but then again it might not if the leakage is neutral to earth. Sometimes its not just one appliance, its the combination of several small earth leakages that trips the RCD. Particularly suspect anything that is closely associated with water Kettles CH water pumps Junction boxes exposed to the elements

Reply to
Graham.

Not necessarily true. A neutral-earth short anywhere in the installation (or an appliance) could cause the reported symptoms. Isolating individual final circuits would not help in this case, unless the OP has double-pole MCBs (unlikely).

So do you, judging by your reply above. Anyway it's fairly rare for RCDs to become defective and when they do fail they tend to become insensitive, or won't trip at all, rather then becoming over-sensitive.

A faulty appliance is the most likely cause. Start with washing machine, dishwasher, fridge & freezer (esp. if frost-free type), immersion heater, toaster. Unplug or isolate these completely, such that the neutral is disconnected too.

Reply to
Andy Wade

Have you got a dishwasher? Ours had something go wrong with it recently and three times had tripped the main RCD - leaving a smell of "burnt" in the kitchen briefly. We'd suspected it might be dishwasher as it'd been finished but still on twice so put the garden RCD onto the plug. Third time it went that RCD had tripped as well as the main house one so BF's dad had a look (ex-repairman) and spotted the problem. Couple of quid for a new bit a interference suppression capacitor thats on the mains side of the switch and so didn't matter if the dishwasher was on or off (as it was the last time) as it had arced across.

Reply to
Mogga

Ok all thanks for the ideas is switching of a circuit at the MCB enough to issoloate everything on that leg or not I am suspicious of a freezer in the garage but having turned off the seperate consumer panel there had discounted that are we now saying I should have unplugged the freezer to test this idea?

Reply to
Mano

Computers and related equipment can cause problems. UPSs as well. Have you recently got a new PC?

Peter Scott

Reply to
Peter Scott

Or a washing machine ?

It's a very common failure. Usually the capacitor is integral with a couple of inductors potted in a metal can to make a filter. Washing type machines draw a high current, the inductors heat up the capacitor and shorten it's life. It seems to be difficult to make a reliable one to fit in the small space they've got at the price they want to pay.

DG

Reply to
Derek Geldard

Here:

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Reply to
John Rumm

If you switched off the main switch in the garage CU (double pole) then you have eliminated everything fed off it.

Reply to
Graham.

And immersion heater, if you have one. A previous house of ours had a corroded immersion heater and it did just this (as it should).

Reply to
Bob Eager

Interesting option we do have one but its turned off never used. Does that rule it out ?

Reply to
Mano

Our dishwasher was plugged in "on" at the wall but not actually on at the machine...

Reply to
Mogga

Depends, I guess. But they usually have a double pole switch, which

*would* rule it out completely.
Reply to
Bob Eager

with was when a column of ants decided to march into my central heating wiring centre (actually just a JB). I eventually found a number of them fused together forming a bridge between L&E. Took me quite some time to find it though.

Reply to
Graham.

Bear in mind that this will not catch a neutral-to-earth fault though. If the RCD is tripping with no other signs of problems ( bangs etc.!) , N-to-E shorting somewhere is a distinct possibility

Reply to
Mike Harrison

I recently had the unpleasant job of removing a partically decomposed mouse from inside my consumer unit. It was evidently providing just the right resistance between live and earth to cause a trip every day or so. The smell gave it away in the end.

Reply to
Calvin

Hi Re the problem check the fridge. freezer .Pains in the backside for this kind of tripping when getting older ,everytime the compressor starts out goes the breaker.

As for strange had similar problems with ants in a call system last year ,took ages to trace .Seems they liked the junction box as a nest.

CJ

Reply to
cj

Ok for completion went round unplugging all none essential items which stopped the tripping re-introduced one at a time over a few days. Proved to be a combination of a deep fat frier (pluged in turned off) and microwave when in the same double socket. different sockects cleared it! wouldnt mind but the deep fat frier was borrowed to test a new recipe and I didnt like it anyway!

Reply to
Mano

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